Weakly Geometric Rough Paths #
This file gives the named weakly geometric rough path layer. In the current library this is the algebraic, group-like signature-valued notion: increments satisfy Chen's identity and the shuffle identities. The metric closure definition of geometric rough paths can be added once the corresponding topology on truncated tensor algebras is available.
Main definitions #
WeakGeometricRoughPath- weakly geometric rough paths as group-like word signature incrementsControlledWeakGeometricRoughPath- weakly geometric rough paths equipped with coordinate bounds by a control
A weakly geometric rough path is a Hopf rough path over the word shuffle Hopf algebra: increments are characters — group-like signature series — and Chen's identity is convolution in the character monoid.
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The underlying group-like algebraic rough path.
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- RoughPaths.WeakGeometricRoughPath.instCoeAlgebraicRoughPath = { coe := fun (X : RoughPaths.WeakGeometricRoughPath T α R) => X.toAlgebraic }
Regard an algebraic group-like rough path as weakly geometric.
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Weakly geometric rough paths are equivalent to group-like algebraic ones.
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The constant identity weakly geometric rough path.
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Pull a weakly geometric rough path back along a map of time domains.
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Pull a weakly geometric rough path back along a map of alphabets.
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Signature increment of a weakly geometric rough path.
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- X.increment s t = X.toAlgebraic.increment s t
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Coordinate of a weakly geometric rough path increment on a word.
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- X.coeff s t word = X.toAlgebraic.coeff s t word
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Truncated signature increment of a weakly geometric rough path.
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- X.truncatedIncrement n s t = X.toAlgebraic.truncatedIncrement n s t
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Agreement of weakly geometric rough paths through word degree n —
the generic graded agreement of Hopf rough paths for the word-length
grading.
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Truncated log-signature increment of a weakly geometric rough path.
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- X.logIncrementTruncated s t n = X.toAlgebraic.logIncrementTruncated s t n
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A controlled weakly geometric rough path with a word-coordinate bound.
- toControlled : AlgebraicRoughPath.Controlled T α R size gauge
- isWeaklyGeometric : self.toControlled.toAlgebraic.IsWeaklyGeometric
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- RoughPaths.ControlledWeakGeometricRoughPath.instCoeControlled = { coe := fun (X : RoughPaths.ControlledWeakGeometricRoughPath T α R size gauge) => X.toControlled }
Regard an algebraically controlled rough path as controlled weakly geometric.
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- RoughPaths.ControlledWeakGeometricRoughPath.ofControlled X hX = { toControlled := X, isWeaklyGeometric := hX }
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Controlled weakly geometric rough paths are equivalent to controlled group-like algebraic ones.
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Forget the analytic control and keep the weakly geometric rough path.
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Underlying algebraic rough path.
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The control attached to a controlled weakly geometric rough path.
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- X.control = X.toControlled.control
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Signature coordinate of a controlled weakly geometric rough path.
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- X.coeff s t word = X.toControlled.coeff s t word
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Truncated increment of a controlled weakly geometric rough path.
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- X.truncatedIncrement n s t = X.toWeakGeometric.truncatedIncrement n s t
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Pull a controlled weakly geometric rough path back along a map of alphabets.
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Pull a controlled weakly geometric rough path back along a monotone time map.
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Agreement through degree n for the underlying weakly geometric rough paths.
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- X.AgreeUpToDegree Y n = X.toWeakGeometric.AgreeUpToDegree Y.toWeakGeometric n